FIGURE 7.

Rhythmic and synchronous activation of slow muscle is perturbed in cx39.9 mutants. A–D, electrophysiological recordings of synaptic inputs (current, A and C; membrane potential, B and D) to slow muscles. Synaptic inputs to slow muscle fibers were cyclic in wild-type (A and B) but arrhythmic in mutants (C and D). E–J, simultaneous observation of Ca²⁺ transients and muscle contractions. E–G, simultaneous increase in cytosolic Ca²⁺ was observed in many wild-type slow muscle fibers. Myotomal borders are depicted by dotted lines (H–J). A Ca²⁺ transient was seen only in a single mutant slow muscle cell (arrow). Contraction by the single fiber led to distortion of the myotome (wavy dotted line in I).